In mould-string foundry plants of this kind it is known to produce the moulds one at a time in the mould-making stations and deliver the produced moulds to a precision conveyor, advancing the moulds stepwise to a pouring station, in closely juxtaposed position forming a mould string with casting cavities at the mainly vertical parting surfaces between successive moulds. Each step in the stepwise advancement of the mould string corresponds to the length occupied by one mould and the mould cavities are filled with molten metal one at a time in the pouring station. The advancing of the moulds is partly performed by the mould-making station pushing a produced mould against the mould string, partly by advancing the precision conveyor, on which the mould string is positioned. The time available for the pouring is the standstill period for the stepwise advancement of the mould string, said standstill period being closely related to the production time for the mould-making machine. In order to increase the time for pouring the moulds, it has been suggested, e.g. in WO 02/26427, to keep the mould string stationary for the time used for producing two moulds in the mould-making station, and having each step in the stepwise advancement of the mould string correspond to the length occupied by two moulds. In this connection the pouring station has been indicated to comprise two pouring outlets for filling two consecutive mould cavities in the mould string.